With the breakthrough in the third generation of semiconductor material gallium nitride, and the advent of blue, green, white light emitting diode (LED), LED, which have a reputation for being the technology to illuminate the future, is walking into our lives and will guide us to illuminating light source. LED light source is a kind of new generation of light source. Primarily, a white LED can be obtained by the following methods: 1. coordinating blue LED with yellow fluorescence powder to produce white light; 2. encapsulating chips of different chromatic lights to produce white light by mixing different chromatic lights; and 3. excitation tricolor fluorescence powders by ultraviolet LED to produce white light.
At present, from the point of technology and application, white LED on the market is the white LED obtained by coordinating blue LED with yellow fluorescence powder. Because the white LED mainly contains blue light and lacks red light which presents a cool color, and color rendering index is lower, the application area of it is greatly limited. Encapsulating chips of different chromatic lights is provided. There are many disadvantages in practical promotion because the driver circuits of chips are complicated. Excitation tricolor fluorescence powders by using ultraviolet LED, producing white light by mixing different chromatic lights, can obtain LED light source with higher color rendering index, which is research hotspot. In tricolor fluorescence powders, green fluorescence powder with high luminous efficiency is used as sulfide fluorescence material, which has the problem that stability is not high enough. LED chips have an advantage of long lifespan, however, the lifespan of LED light source will be certainly affected because the stability of the used fluorescence material is not good.